Telecom engineering reference for protocols, messages, call flows, troubleshooting, releases, and tools.
Menu
LTE RRCLTEeNodeB -> UE3GPP TS 36.331
LTE RRC Mobility From EUTRA Command
Downlink LTE RRC message used to command mobility away from the current E-UTRA connection toward another RAT or a cell change order outcome.
Message Fact Sheet
Protocol
lte-rrc
Network
lte
Spec
3GPP TS 36.331
Spec Section
5.4.3, 6.2.2
Direction
eNodeB -> UE
Message Type
Mobility Control
Full message name
LTE RRC Mobility From EUTRA Command
Protocol
LTE-RRC
Technology
LTE
Direction
eNodeB -> UE
Interface
Uu
Signaling bearer / channel
SRB1 / DL-DCCH
Typical trigger
The network has decided to move the UE out of the current LTE serving context toward UTRA, GERAN, cdma2000, NR, another E-UTRA target, or an enhanced CS fallback branch.
Main purpose
Carries the target-RAT command and mobility intent when the network wants the UE to leave the current LTE serving context for inter-RAT handover, cell change order, or enhanced CS fallback.
What is LTE RRC Mobility From EUTRA Command in simple terms?
Downlink LTE RRC message used to command mobility away from the current E-UTRA connection toward another RAT or a cell change order outcome.
Carries the target-RAT command and mobility intent when the network wants the UE to leave the current LTE serving context for inter-RAT handover, cell change order, or enhanced CS fallback.
Why this message matters
MobilityFromEUTRACommand is the LTE message that tells the UE to leave the current LTE serving cell and continue on another mobility path.
Where this message appears in the call flow
Inter-RAT handover from LTE
In the inter-RAT handover path, MobilityFromEUTRACommand is the LTE downlink mobility command that carries the target-RAT transition information.
Call flow position: Network mobility command sent after the inter-RAT target decision is complete and the UE must leave the current LTE serving cell.
Typical state: UE is in RRC_CONNECTED and is being commanded toward another RAT or target mobility outcome.
Preconditions:
A mobility decision has already been made.
The target RAT information is ready for delivery to the UE.
Next likely message: Target RAT access or handover continuation
GERAN cell change order
In a GERAN cell change order case, MobilityFromEUTRACommand carries the branch that moves the UE out of LTE toward GERAN.
Call flow position: Dedicated mobility command used when the UE is ordered from LTE toward GERAN using cell change order handling.
Typical state: UE is still in the LTE connected context just before leaving for the GERAN branch.
Preconditions:
The network selected GERAN as the next mobility target.
The cell change order information is available.
Next likely message: GERAN acquisition and later access signaling
Enhanced CS fallback
In enhanced CS fallback, MobilityFromEUTRACommand is the LTE mobility command that starts the target-system continuation for CS service.
Call flow position: Mobility command branch used when the UE is moved out of LTE for CS service continuation.
Typical state: UE is in connected LTE signaling and the voice-related fallback decision has already been made.
Preconditions:
CS service continuation is needed.
The e-CSFB command content is available where applicable.
Next likely message: Target-system access for CS service continuation
The main reading path is the purpose branch and the targetRAT-Type. That tells you whether the command is a normal inter-RAT handover, a cell change order, or an enhanced CS fallback case.
LTE RRC Mobility From EUTRA Command - Example Dump
Start with the purpose branch because that tells you which mobility path the command is taking.
Check targetRAT-Type next because it defines the next system the UE should move toward.
If the path is voice-related, check cs-FallbackIndicator and whether the branch is e-CSFB.
Treat the targetRAT-MessageContainer as the handover payload boundary that explains the target-side continuation.
Important Information Elements
IE
Required
Description
rrc-TransactionIdentifier
Yes
Transaction identifier used to correlate the mobility command procedure.
cs-FallbackIndicator
Yes
Boolean flag showing whether the command is tied to CS fallback handling.
purpose
Yes
Main mobility branch indicating handover, cell change order, or enhanced CS fallback content.
targetRAT-Type
Optional
Target RAT indicated inside the handover or cell-change structure.
targetRAT-MessageContainer
Optional
Target-system mobility or handover information delivered to the UE.
bandIndicator
Optional
GERAN-related band information carried in later extension branches when needed.
Detailed field explanation
rrc-TransactionIdentifier
Transaction identifier used to correlate the mobility command procedure.
Presence: Required
In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.
cs-FallbackIndicator
Boolean flag showing whether the command is tied to CS fallback handling.
Presence: Required
In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.
purpose
Main mobility branch indicating handover, cell change order, or enhanced CS fallback content.
Presence: Required
In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.
targetRAT-Type
Target RAT indicated inside the handover or cell-change structure.
Presence: Optional
In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.
targetRAT-MessageContainer
Target-system mobility or handover information delivered to the UE.
Presence: Optional
In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.
bandIndicator
GERAN-related band information carried in later extension branches when needed.
Presence: Optional
In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.
What to check in logs and traces
Confirm the message follows a real mobility decision and not a normal connected-mode update.
Check whether the purpose is handover, cellChangeOrder, or e-CSFB-r9.
Inspect targetRAT-Type and correlate it with the expected target-system behavior.
Check whether T304 starts and whether the UE leaves LTE as expected.
Follow the trace into the target RAT instead of stopping at the LTE command.
Common Issues and Troubleshooting
The command is present but the UE never completes the expected target move.
Likely cause: The target-side mobility payload may be wrong, incomplete, or inconsistent with the actual target environment.
What to inspect: Check the purpose branch, targetRAT-Type, targetRAT-MessageContainer, and the immediate target access behavior.
Next step: Continue into the target RAT trace and compare against a known-good inter-RAT mobility case.
The command appears during voice fallback but service still drops.
Likely cause: The enhanced CS fallback branch may have been triggered correctly, but the target system access may have failed afterward.
What to inspect: Check cs-FallbackIndicator, the e-CSFB branch, and the target-side access or paging behavior.
Next step: Treat this as a mobility-continuation problem, not only an LTE message decode issue.
The UE leaves LTE but the target system is different from what was expected.
Likely cause: The purpose branch or target RAT information may indicate a different mobility decision than assumed.
What to inspect: Validate targetRAT-Type, any GERAN-specific band information, and the target-side signaling that follows.
Next step: Align the expected mobility target with what the command actually carried.
LTE / 5G / Variant Comparison
Compared with RRCConnectionReconfiguration
RRCConnectionReconfiguration changes the connected LTE context while the UE stays on LTE. MobilityFromEUTRACommand tells the UE to leave the current LTE context toward another target outcome.
Compared with RRCConnectionRelease
RRCConnectionRelease ends the LTE connected context, often toward idle or redirection. MobilityFromEUTRACommand is an explicit connected-mode mobility command toward another RAT or mobility branch.
FAQ
What is MobilityFromEUTRACommand in LTE?
It is the downlink LTE RRC mobility command that tells the UE to leave the current LTE serving context toward another RAT or mobility outcome.
What should I inspect first in MobilityFromEUTRACommand?
Start with the purpose branch, then check targetRAT-Type and the immediate target-system behavior after the command.
Is MobilityFromEUTRACommand the same as RRCConnectionRelease?
No. RRCConnectionRelease ends the LTE connected context, while MobilityFromEUTRACommand is an explicit mobility command toward another target path.
Why is this message important in trace analysis?
It marks the point where the LTE connected trace hands control to the target mobility branch, so it explains why the UE leaves LTE and what should happen next.
Decode this message with the 3GPP Decoder, inspect the related message database, or open the matching call flow to see where this signaling step fits in the full procedure.
